Install New Thyristor; Fasten The Clamp - ABB DCS 500B Service Manual

Install new thyristor

Fasten the clamp

DCS 500 / DCS 600 Service Manual
- Ensure that the new thyristor is of the correct type
dix A). Keep the semiconductor and its surroundings clean. If
necessary clean them with a piece of tissue paper moistened
with solvent. Make sure the insulator of the thyristor and the con-
nections are fine.
Note: Do not touch the polished surfaces of the thyristor.
- Clean the polished surfaces of the semiconductor with a piece of
tissue paper moistened with solvent. Dry all surfaces. Spread a
thin layer of heat conducting paste on both sides of the thyristor,
if necessary use a rubber spatula.
- Clean all parts with tissue paper moistened with solvent, witch
have had or will have contact with the thyristor or each other
(bottom of upper heat sink, busbar on both sides and upper side
of the DC and AC busbar). Do not clean the surfaces of grease
too thoroughly, because the aluminium surfaces will oxidise in a
few seconds. Dry all surfaces.
- Connect the gate leads if possible.
- Place the thyristor with the right direction into the guiding tool.
Spread the head conducting paste by turning the thyristor 90° left
and right.
Note: Do not pinch or cut the gate leads or any other cable.
- Turn the thyristor so that the gate leads point in the right direc-
tion.
- Spread a thin layer of Molikote (MSO
the lower side of the head of each of the srews, keeping the heat
sink by means of the press clamp in place. Spread Molikote also
on the side of the washers, which comes in contact with the
screw. Spread a thin layer of heat conducting paste on the bot-
tom of the heat sink with a rubber spatula. Place the busbar and
the heat sink above the thyristor and fix them with the press
clamp. Tighten the clamping screws by hand until the screw
heads touch the bottom of the module.
3ADW000093R0701_DCS500B/DCS600_Service manual_e_g
Chapter 8 - Exchange of Thyristors for Size C3
) on the thread and under
2
Molikote
(see Appen-
VI A
8 - 3